As the most common male carcinoma, prostate cancer is a major tumor entity in oncology. In addition to definitive radiotherapy, surgical procedure is considered to be an oncologically equivalent therapeutic alternative for non-metastatic malignancies in the primary setting. However, a subsequent radiotherapy of the prostate bed is often necessary, which takes place as an "adjuvant" treatment immediately after surgery or in the course of a repeated increase in PSA and usually extends over several weeks. For the primary situation (without previous surgery), several randomized phase III clinical trials have shown that it is possible to shorten radiotherapy by increasing the single dose (called hypofractionation). In the context of two prospective Phase II studies, which were carried out in Heidelberg, it has since been shown that hypofractionation with both photons and protons is safe and feasible even in the postoperative situation.

The current, prospective and randomized PAROS study is now intended to demonstrate a multicentric phase III study as an improvement in the quality of life caused by rectum toxicity (primary endpoint) by the use of protons. The oncological non-inferiority of hypofractionated radiotherapy after surgery is a secondary endpoint.

Inclusion Criteria:

• histology-proven prostate cancer with Gleason Score and PSA-value;
• indication for prostate bed irradiation (adjuvant/ salvage) after prostatectomy;
• Karnofsky-Index ≥ 70%
• age ≥ 18 years

Exclusion Criteria:

• androgen deprivation therapy
• lymphatic spread
• macroscopic tumor/ R2
• stage IV (M1)
• previous irradiation